Wastewater-based Surveillance
on SARS-CoV-2

AMELAG - Weekly report
09.10.2024


The SARS-CoV-2 viral load in wastewater is being tested at selected wastewater treatment plants (WWTP) in Germany as part of AMELAG (“Abwassermonitoring für die epidemiologische Lagebewertung”, German for wastewater monitoring for epidemiological situation assessment). Data from 168 WWTP are currently included in the analyses. For the calendar week 40 data from 84 WWTP were available. Data from other WWTP are provided continuously.

The COVID-19 situation is assessed comprehensively in the weekly report on acute respiratory diseases (ARE weekly report) together with other indicators. A comparison between the aggregated SARS-CoV-2 viral load in wastewater and the COVID-19 incidence is shown in the weekly Grippeweb report.

The course of the viral loads aggregated across all sites is shown in Figure 1 in order to obtain an overall picture of the mean viral load and its development in Germany. To this end, weekly mean values of the viral loads (given in gene copies/liter), previously transformed by the common logarithm, are computed, first for each site and then across all sites for the respective week. The mean values are weighted according to the number of inhabitants connected to the respective site. The estimation of the regression curve is also weighted, so that weekly mean values with higher uncertainty are given a lower weight in the estimation and vice versa. A steep increase in the aggregated SARS-CoV-2 viral load can be observed for the last two weeks. The development observed over the last few weeks may still change due to late notifications, especially from WWTP with large population coverage.

Figure 1: Aggregated SARS-CoV-2 load in wastewater over time (grey dots) along with regression curve (black line, estimated using the LOESS method) and associated 95% confidence intervals (light blue area). The data was last updated on Tuesday the 08.10.2024, 10 am. The latest data used in the calculations is from the previous Wednesday’s sampling (02.10.2024, CW 40). Shown are 7-day averages, which refer to the period from Thursday to Wednesday; the most recent value is calculated from the data from 26.09.2024 (CW 39), to 02.10.2024 (CW 40). The date of the sample corresponds to the start date of the 24-hour composite sample.
The time period displayed can be adjusted using the buttons on the top left. The button on the right allows you to display the data points, regression curve and confidence intervals on the logarithmic scale or transformed back to the original scale. It should be taken into account when interpreting the data that changes in viral loads in the low value range are emphasized more strongly than values in the high value range on a logarithmic scale. By hovering over the individual points the calendar week, the date of the corresponding Wednesday, the viral load, the number of sites and the proportion of the total population that is included in the calculation at that time are shown.
Only data from sites for which data is available from the last five calendar weeks is included. The number of sites included at each point in time may differ between the figures, as the sites with fewer than 10 data points are not included in all figures.
Data for further sites will be supplied subsequently.

Additionally, the course of the viral load in wastewater is shown for the individual WWTPs in Figure 2.

Figure 2: SARS-CoV-2 load in wastewater over time (grey dots) along with the regression curve (black line, estimated using the LOESS method) and associated 95% confidence intervals (light blue area). The data was last updated on 08.10.2024, 10 am. The date of the sample corresponds to the start date of the 24-hour composite sample.
The location can be selected using the filter and the time period displayed can be adjusted using the buttons on the top left. The button on the right allows you to display the data points, regression curve and confidence intervals on the logarithmic scale or transformed back to the original scale. Changes in viral loads in the low value range are easier to recognize on a logarithmic scale. By hovering over the individual points the calendar week, date of sampling and viral load are shown.
Those sites for which data is available within the last five calendar weeks are shown. For sites with fewer than 10 data points, only the individual data points are shown. The corresponding regression curves and confidence intervals will be calculated when at least 10 data points are available.
Changes in laboratory or changes in the methods used in laboratories are indicated with a dashed, vertical line.
Data from other sites will be supplied subsequently.

Trends for the viral load in the wastewater can be calculated from the regression curves in Figure 2 for each WWTP. These trends are shown in Figure 3. For the calendar week 40 a trend could be calculated for 8 sites. For 4 sites, the trend indicates an increasing viral load.

All

BB

BE

BW

BY

HB

HE

HH

MV

NI

NW

RP

SH

SL

SN

ST

TH

Figure 3: Change in SARS-CoV-2 load in wastewater per site.
Trend categories: “increasing” (defined as an increase of more than 15% compared to the previous week), “unchanged” (change between -15% and 15% compared to the previous week) and “decreasing” (decrease of more than 15% compared to the previous week).
The data was last updated on 08.10.2024, 10 am. The most recent data included in the trends calculated here is from the previous Wednesday’s sampling (02.10.2024, CW 40). The date of the sample corresponds to the start date of the 24-hour composite sample. As the trend is calculated as the change in the (smoothed) viral load compared to the previous week’s value, the calendar week 40 describes the period from Wednesday, the 25.09.2024 (CW 39), to Wednesday, the 02.10.2024 (CW 40). Shown are sites which supplied at least 10 data points within the last five calendar weeks. Sites that have already provided data but fewer than 10 data points include. Since sites with fewer than 10 data points are not included in this figure, but are included in the calculations for Figure 1, the number of sites included at a point in time may differ between the figures.
Changes in laboratory or changes in the methods used in laboratories are indicated with a dashed, vertical line.
Data for other sites will be supplied subsequently.

The geographical locations, along with the most recent trend of those WWTPs that have already delivered data are shown in Figure 4.


Figure 4: Map of the WWTPs showing the trend of the viral load per site.

The following WWTPs already provide data and will be included in all calculations as soon as at least 10 data points are available: Germersheim .

In AMELAG, wastewater samples from 8 WWTPs / sampling sites are also sequenced and analyzed by the Technical University of Darmstadt as cooperation partner. This allows the relative increase or decrease (Frequency in %) of already known variants to be determined (Figure 5).

According to the WHO classification, the SARS-CoV-2 variants BA.2.86 and JN.1 are currently considered as variants of interest (VOIs) and the variants JN.1.7, KP.2, KP.3, KP.3.1.1, JN.1.18, LB.1 and XEC are considered as variants under monitoring (VUMs). All current VUMs are derived from JN.1.

The proportion of KP.3.1.1 in particular has increased since calendar week 24 2024. The newest variant classified as a VUM, XEC, has been detected at the sampled sites since calendar week 37.

Figure 5: Percentage of current SARS-CoV-2 variants of interest (VOI) and SARS-CoV-2 variants under observation (VUM). The percentages also include all respective sublines of a variant, with the exception of the sublines specifically listed here. For example, BA.2.86 does not include the relative proportions of JN.1 and its sublines. The results of the sampling of 8 WWTPs / sampling sites are shown since calendar week 35 2023, as far as the data are available. The selection of the sublines shown is based on the WHO classification. Further explanations of the classification can be found on the integrated genomic surveillance page. The analysis is based on the Freyja bioinformatics tool and is therefore dependent on the Freyja reference used to identify SARS-CoV-2 variants.

Background

In the case of some infectious diseases, infected persons excrete the pathogens in their stool. Laboratories can examine the wastewater and detect the pathogens there. This allows the spread of these pathogens to be monitored.

In the project AMELAG SARS-CoV-2 is monitored in wastewater. Nationwide, 168 WWTP are taking part. In addition to SARS-CoV-2, other pathogens will also be investigated. The Federal Environment Agency and the Robert Koch Institute are working together with the Bundeswehr Medical Service, the health and environmental authorities of the federal states, laboratories, universities and the operators of the WWTP. The project is funded by the Federal Ministry of Health.

The data shown here originate from the projects AMELAG, ESI-CorA, COVIDready, Sars-GenASeq, Wastewater Biomarker CoV-2 and projects funded by the federal states. ESI-CorA was funded by the European Commission as part of the Emergency Support Instrument (ESI) (No 060701/2021/864650/SUB/ENV.C2). COVIDready, Sars-GenASeq and Wastewater Biomarker CoV-2 were funded by the Federal Ministry of Education and Research.

The methods are described in the technical guidelines 1 - 4 at http://www.rki.de/abwassersurveillance.

Data and software code from the AMELAG project are published on Zenodo and GitHub.

The processes and possible applications for wastewater surveillance are described in the Epidemiological Bulletin 34/2024.

Limitations

Wastewater data do not allow any conclusions to be drawn about the severity of the disease or the burden on the healthcare system. As things stand, wastewater data cannot be used to draw precise conclusions about incidence/prevalence or underreporting. The data should always be considered in conjunction with other indicators, e.g. from syndromic surveillance in order to asses the situation epidemiologically.

Absolute viral loads cannot be compared directly with regard to the number of infected persons, especially over longer periods of time, as the amount of virus excreted per infected person can differ between different virus variants, for example.

The values determined are influenced by a variety of factors (e.g. changes in the waste water supply, heavy rainfall events or tourist events), which can only be partially compensated for by normalization.

Suggested citation
Robert Koch-Institut, Umweltbundesamt: AMELAG-Weekly Report CW 41/2024 | DOI: 10.25646/12874

Contact

Robert Koch-Institut
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13353 Berlin

Email:
WEB: http://www.rki.de/abwassersurveillance

Umweltbundesamt
Wörlitzer Platz 1
06844 Dessau-Roßlau

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